The present invention relates to a connector for fiber optics.
More precisely, the object of the invention is a connector of the type having two ferrules mounted on the end of each of the fibers to be connected and each having a bore into which the fiber optic can be inserted loosely and fixed such that its end coincides with the end of the ferrule, a female reconstitution coupling having a longitudinal bore to hold an align the two ends in abutment, and longitudinal pressure means to push each of the ferrules toward the other.
Radiall S. A. has already described, in EP-A-0063085, a connector of this type wherein the female coupling has in its central part, inside of its longitudinal bore, an abutment body for the male ferrules, particularly a sphere, having an axial through-bore and around the latter a bearing contact surface facing each of the male ferrules. Each of the male ferrules has an axial tubular protuberance which can be engaged in the bore in the abutment body, the end of the fiber coinciding with the end of the protuberance. Each of the ferrules has, set back from the protuberance and surrounding the rear portion thereof, annular recess whose wall, preferably of conical profile, defines a bearing surface for contact with the confronting bearing surface of the abutment body of the female connector, and the bearing surfaces in contact are pressed against one another by the action of longitudinal pressure means. The confronting bearing surfaces of the male ferrules are configured such that, upon any relative movement of the bearing surfaces in contact, the end of a fiber at the end face of the protuberance of a male ferrule, will be held at a constant, predetermined distance from the center of the abutment body.
The end faces of the protuberances of the ferrules and of the fibers fixed inside of them are straight, that is, perpendicular to the longitudinal axis of the connector, or they can be inclined with respect to this axis when an attenuating function is sought, as described for example in French application FR-A-2598820 of Radiall S. A.
In all cases, the end faces of the confronting fibers are not in contact with one another but are separated by a gap which, in practice, is on the order of 6 to 15 micrometers once the connection is made. In fact, a larger gap, particularly one greater than 25 micrometers, would create unacceptable losses at the connection.
There is therefore an air gap between the ends of the confronting fiber optics.
Now, the refractive index of air differs quite perceptibly from that of the core of the silica optical fibers presently used, which have a refractive index of 1.47.
In order to avoid Fresnel losses by reflection upon passing through the layer of air between the ends of the confronting fibers, it in known to replace the space between the confronting fiber ends with a product of a greasy or gel consistency called an "index gel", which has an index of refraction equal to or close to that of the core of the fibers. An example thereof is given in GS-A-2056705.
In connectors of the type described in EP-A-0063085, before putting the ferrules into the female connector, a small amount of index gel is put onto the end face of the ferrule at which the fiber is exposed, and then the ferrules are fixed in the female connector.
This method is not satisfactory because, on the one hand, it happens in practice that the technician making the connection neglects to install the index del, and on the other hand the gel tends to evaporate during use. Moreover, when the connection must be taken apart and reassembled it is necessary to clean the end faces of the ferrules so as to remove the residual gel, and then to put on another application of index gel.
The present invention proposes to eliminate the problems connected with the use of an index gel between the confronting end faces of the fibers being connected.